8/13/2019 How to Troubleshoot Ecu Control http://slidepdf.com/reader/full/how-to-troubleshoot-ecu-control 1/17 HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS A large number of ECU controlled systems are used in the TACOMA. In general, the ECU controlled system is considered to be a very intricate system requiring a high level of technical knowledge and expert skill to troubleshoot. However, the fact is that if you proceed to inspect the circuits one by one, troubleshooting of these systems is not complex. If you have adequate understanding of the system and a basic knowledge of electricity, accurate diagnosis and necessary repair can be performed to locate and fix the problem. This manual is designed through emphasis of the above standpoint to help service technicians perform accurate and effective troubleshooting, and is compiled for the following major ECU controlled systems: The troubleshooting procedure and how to make use of it are described on the following pages. 4. Supplemental Restraint System 2. A340E, A340F Automatic Transmission 2RZ−FE, 3RZ−FE Engine 3. Anti−Lock Brake 5. Cruise Control 5VZ−FE Engine Repair Manual EG1−188 System EG2−216 AT2−42 BR−51 RS−25 BE−96 Vol. 2 Vol. 1 Page − INTRODUCTION HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS IN−13
HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS A large number of ECU controlled systems are used in the TACOMA In general the ECU controlled system
is considered to be a very intricate system requiring a high level of technical knowledge and expert skill to
troubleshoot However the fact is that if you proceed to inspect the circuits one by one troubleshooting of
these systems is not complex If you have adequate understanding of the system and a basic knowledge of
electricity accurate diagnosis and necessary repair can be performed to locate and fix the problem This
manual is designed through emphasis of the above standpoint to help service technicians perform accurateand effective troubleshooting and is compiled for the following major ECU controlled systems
The troubleshooting procedure and how to make use of it are described on the following pages
4 Supplemental Restraint System
2 A340E A340F Automatic Transmission
2RZminusFE 3RZminusFE Engine
3 AntiminusLock Brake
5 Cruise Control
5VZminusFE Engine
Repair Manual
EG1minus188
System
EG2minus216
AT2minus42
BRminus51
RSminus25
BEminus96
Vol 2
Vol 1
Page
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
In troubleshooting the problem symptoms must be confirmed accurately and all preconceptions must be
cleared away in order to give an accurate judgement To ascertain just what the problem symptoms are
it is extremely important to ask the customer about the problem and the conditions at the time it occurred
Important Points in the Problem Analysis
The following 5 items are important points in the problem analysis Past problems which are thought to beunrelated and the repair history etc may also help in some cases so as much information as possible shou
be gathered and its relationship with the problem symptoms should be correctly ascertained for reference
in troubleshooting A customer problem analysis table is provided in the troubleshooting section for each
system for your use
(Sample) Engine control system check sheet
Important Points in the Customer Problem Analysis
bull What Vehicle model system name
bull When Date time occurrence frequency
bull Where Road conditions
bull Under what conditions Running conditions driving conditions weather conditions
bull How did it happen Problem symptoms
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
In diagnostic trouble code check it is very important to determine whether the problem indicated by thediagnostic trouble code is still occurring or occurred in the past but returned to normal at present In addiminustion it must be checked in the problem symptom check whether the malfunction indicated by thediagnostic trouble code is directly related to the problem symptom or not For this reason the diagnostictrouble codes should be checked before and after the symptom confirmation to determine the current condtions as shown in the table below If this is not done it may depending on the case result in unnecessarytroubleshooting for normally operating systems thus making it more difficult to locate the problem or inrepairs not pertinent to the problem Therefore always follow the procedure in correct order and performthe diagnostic trouble code checkDIAGNOSTIC TROUBLE CODE CHECK PROCEDURE
2 SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE CHECK
The diagnostic system in the TACOMA fulfills various functions The first function is the Diagnostic Trouble
Code Check in which a malfunction in the signal circuits to the ECU is stored in code in the ECU memory at
the time of occurrence to be output by the technician during troubleshooting Another function is the Input
Signal Check which checks if the signals from various switches are sent to the ECU correctly The air condiminus
tioner system has an Actuator Check function whereby the ECU automatically operates the actuators of thedamper and blowermotor etc to check the operation By using these check functions the problem areas
can be narrowed down quickly and troubleshooting can be performed effectively Diagnostic functions are
incorporated in the following systems in the TACOMA
The problem is still occurring in a place otherthan in the diagnostic circuit(The diagnostic trouble code displayed first iseither for a past problem or it is a secondaryproblem)
The problem is still occurring in a place otherthan in the diagnostic circuit
The problem occurred in a place other than inthe diagnostic circuit in the past
The problem occurred in the diagnostic circuitin the past
Problem is still occurring in the diagnosticcircuit
Diagnostic TroubleCode Check (Make anote of and thenclear)
Supplemental Restraint System
Same diagnostictrouble code isdisplayed
Normal code isdisplayed
Other DiagnosisFunction
Input Signal Check(Sensor Check)
Diagnostic TroubleCode Check
Diagnostic TroubleCode Check
Problem Condition
Diagnostic TroubleCode Display
No problemsymptoms exist
Confirmation ofSymptoms
Problem symptomsexist
Problem symptomsexist
Normal code isdisplayed
No problemsymptoms exist
Normal code isdisplayed
Automatic Transmission O (with Check Mode)
O (with Check Mode)
O (with Check Mode)
Diagnostic Test Mode
Diagnostic Test Mode
Diagnostic Test Mode
Normal Code Display
2RZminusFE 3RZminusFE
System
Engine
5VZminusFE
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
Taking into account the above points a flow chart showing how to proceed with troubleshooting using the
diagnostic trouble code check is shown below This flow chart shows how to utilize the diagnostic trouble
code check effectively then by carefully checking the results indicates how to proceed either to diagnostic
trouble code troubleshooting or to troubleshooting of problem s^mptoms
If a diagnostic trouble code was disminus
played in the initial diagnostic troublecode check it indicates that the troublemay have occurred in a wire harness orconnector in that circuit in the pastTherefore check the wire harness andconnectors (see page INminus24)
Troubleshooting of problemindicated by diagnostic trouminusble code
bull Normal code displayedbull Problem symptoms exist
bull Diagnostic trouble codedisplayed
bull Problem symptoms exist
Making a note of and clearing of thediagnostic trouble codes displayed
bull Normal code displayed
bull No problem symptomsexist
Simulation test using the symptomsimulation methods
No problem symptomsexist
Troubleshooting of eachproblem symptom
Symptom confirmation
Diagnostic trouble code check
Diagnostic trouble code check
Problem symptomsexist
System Normal
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The most difficult case in troubleshooting is when there are no problem symptoms occurring In such casesa thorough customer problem analysis must be carried out then simulate the same or similar conditions andenvironment in which the problem occurred in the customerrsquos vehicle No matter how much experience atechnician has or how skilled he may be if he proceeds to troubleshoot without confirming the problem
symptoms he will tend to overlook something important in the repair operation and make a wrong guesssomewhere which will only lead to a standstill For example for a problem which only occurs when theengine is cold or for a problem which occurs due to vibration caused by the road during driving etc theproblem can never be determined so long as the symptoms are confirmed with the engine hot condition orthe vehicle at a standstill Since vibration heat or water penetration (moisture) are likely causes for problemswhich are difficult to reproduce the symptom simulation tests introduced here are effective measures inthat the external causes are applied to the vehicle in a stopped conditionImportant Points in the Symptom Simulation TestIn the symptom simulation test the problem symptoms should of course be confirmed but the problem areaor parts must also be found out To do this narrow down the possible problem circuits according to thesymptoms before starting this test and connect a tester beforehand After that carry out the symptom simminus
ulation test judging whether the circuit being tested is defective or normal and also confirming the problem
symptoms at the same time Refer to the matrix chart of problem symptoms for each system to narrowdown the possible causes of the symptom
PARTS AND SENSORS
Apply slight vibration with a finger to the part of the senminus
sor considered to be the problem cause and check if the
malfunction occurs
HINT Applying strong vibration to relays may result
in open relays
WIRE HARNESS
Slightly shake the wire harness vertically and horizonminus
tally The connector joint fulcrum of the vibration and
body through portion are the major areas to be checked
thoroughly
CONNECTORS
Slightly shake the connector vertically and horizontally
VIBRATION METHOD When vibration seems to be the major cause
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The inspection procedure is shown in the table below This table permits efficient and accuratetroubleshooting using the diagnostic trouble codes displayed in the diagnostic trouble code check Proceedwith troubleshooting in accordance with the inspection procedure given in the diagnostic chart corresponminusding to the diagnostic trouble codes displayed
The engine diagnostic trouble code chart is shown below as an example
bull Page or InstructionsIndicates the page where the inspection prominuscedure for each circuit is to be found or gives inminus
structions for checking and repairs
bull Diagnostic Trouble CodeDetecting ConditionIndicates the diagnostic
trouble code setparameter
bull Detection ItemIndicates the system of the prominus
blem or contents of the problem
bull Trouble AreaIndicates the suspect area of the prominusblem
bull DTC NoIndicates the diagnostic troublecode
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The suspect circuits or parts for each problem symptom are shown in the table below Use this table totroubleshoot the problem when a rdquoNormalrdquo code is displayed in the diagnostic trouble code check but theproblem is still occurring Numbers in the table indicate the inspection order in which the circuits or partsshould be checkedHINT when the problem is not detected by the diagnostic system even though the problem symptom is
present it is considered that the problem is occurring outside the detection range of the diagnostic system
or that the problem is occurring in a system other than the diagnostic system
bull Circuit Inspection Inspection OrderIndicates the circuit which needs to be checked
for each problem symptom Check in the order inminus
dicated by the numbers
bull Circuit or Part NameIndicates the circuit or part which needs to bechecked
bull PageIndicates the page where the flow chart foreach circuit is located
bull Problem Symptom
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE1 For troubleshooting diagnostic trouble code charts or problem symptom charts are provided for each
circuit with detailed inspection procedures on the following pages
2 When all the component parts wire harnesses and connectors of each circuit except the ECU are
found to be normal in troubleshooting then it is determined that the problem is in the ECU
Accordingly if diagnosis is performed without the problem symptoms occurring the instruction will be
to check and replace the ECU even if the problem is not in the ECU So always confirm that the prominus
blem symptoms are occurring or proceed with inspection while using the symptom simulation
method
3 The instructions rdquoCheck wire harness and connectorrdquo and rdquoCheck and replace ECUrdquo which appear in
the inspection procedure are common and applicable to all diagnostic trouble codes Follow the prominus
cedure outlined below whenever these instructions appear
Check Wire Harness and ConnectorThe problem in the wire harness or connector is an open circuit or a short circuit
OPEN CIRCUITThis could be due to a disconnected wire harness faulty contact in the connector a connector terminal pullminus
ed out etc
HINT
1 It is rarely the case that a wire is broken in the middle of it Most cases occur at the connector In par minus
ticular carefully check the connectors of sensors and actuators
2 Faulty contact could be due to rusting of the connector terminals to foreign materials entering terminus
minals or a drop in the contact pressure between the male and female terminals of the connector Simpminus
ly disconnecting and reconnecting the connectors once changes the condition of the connection anc
may result in a return to normal operation
Therefore in troubleshooting if no abnormality is found in the wire harness and connector check but
the problem disappears after the check then the cause is considered to be in the wire harness or con
nectors
SHORT CIRCUITThis could be due to a short circuit between the wire harness and the body ground or to a short inside the
switch etc
HINT
bull When there is a short between the wire harness and body ground check thoroughly whether the wire
harness is caught in the body or is clamped properly
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
(1) Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connecminus
tor (A) and body ground
In the case of Fig 6
Between terminal 1 of connector (A) and body ground rarr Continuity
Between terminal 2 of connector (A) and body ground rarr No continuity (open)Therefore it is found out that there is a short circuit between terminal 1 of connector (A) and terminal
1 of connector (C)
(2) Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body
ground and terminal 1 of connector (B) and body ground
Between terminal 1 of connector (A) body ground rarr No continuity (open)
Between terminal 1 of connector (B) and body ground rarr Continuity
Therefore it is found out that there is a short circuit between terminal 1 of connector (B) and terminal
1 of connector (C)
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
In troubleshooting the problem symptoms must be confirmed accurately and all preconceptions must be
cleared away in order to give an accurate judgement To ascertain just what the problem symptoms are
it is extremely important to ask the customer about the problem and the conditions at the time it occurred
Important Points in the Problem Analysis
The following 5 items are important points in the problem analysis Past problems which are thought to beunrelated and the repair history etc may also help in some cases so as much information as possible shou
be gathered and its relationship with the problem symptoms should be correctly ascertained for reference
in troubleshooting A customer problem analysis table is provided in the troubleshooting section for each
system for your use
(Sample) Engine control system check sheet
Important Points in the Customer Problem Analysis
bull What Vehicle model system name
bull When Date time occurrence frequency
bull Where Road conditions
bull Under what conditions Running conditions driving conditions weather conditions
bull How did it happen Problem symptoms
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
In diagnostic trouble code check it is very important to determine whether the problem indicated by thediagnostic trouble code is still occurring or occurred in the past but returned to normal at present In addiminustion it must be checked in the problem symptom check whether the malfunction indicated by thediagnostic trouble code is directly related to the problem symptom or not For this reason the diagnostictrouble codes should be checked before and after the symptom confirmation to determine the current condtions as shown in the table below If this is not done it may depending on the case result in unnecessarytroubleshooting for normally operating systems thus making it more difficult to locate the problem or inrepairs not pertinent to the problem Therefore always follow the procedure in correct order and performthe diagnostic trouble code checkDIAGNOSTIC TROUBLE CODE CHECK PROCEDURE
2 SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE CHECK
The diagnostic system in the TACOMA fulfills various functions The first function is the Diagnostic Trouble
Code Check in which a malfunction in the signal circuits to the ECU is stored in code in the ECU memory at
the time of occurrence to be output by the technician during troubleshooting Another function is the Input
Signal Check which checks if the signals from various switches are sent to the ECU correctly The air condiminus
tioner system has an Actuator Check function whereby the ECU automatically operates the actuators of thedamper and blowermotor etc to check the operation By using these check functions the problem areas
can be narrowed down quickly and troubleshooting can be performed effectively Diagnostic functions are
incorporated in the following systems in the TACOMA
The problem is still occurring in a place otherthan in the diagnostic circuit(The diagnostic trouble code displayed first iseither for a past problem or it is a secondaryproblem)
The problem is still occurring in a place otherthan in the diagnostic circuit
The problem occurred in a place other than inthe diagnostic circuit in the past
The problem occurred in the diagnostic circuitin the past
Problem is still occurring in the diagnosticcircuit
Diagnostic TroubleCode Check (Make anote of and thenclear)
Supplemental Restraint System
Same diagnostictrouble code isdisplayed
Normal code isdisplayed
Other DiagnosisFunction
Input Signal Check(Sensor Check)
Diagnostic TroubleCode Check
Diagnostic TroubleCode Check
Problem Condition
Diagnostic TroubleCode Display
No problemsymptoms exist
Confirmation ofSymptoms
Problem symptomsexist
Problem symptomsexist
Normal code isdisplayed
No problemsymptoms exist
Normal code isdisplayed
Automatic Transmission O (with Check Mode)
O (with Check Mode)
O (with Check Mode)
Diagnostic Test Mode
Diagnostic Test Mode
Diagnostic Test Mode
Normal Code Display
2RZminusFE 3RZminusFE
System
Engine
5VZminusFE
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
Taking into account the above points a flow chart showing how to proceed with troubleshooting using the
diagnostic trouble code check is shown below This flow chart shows how to utilize the diagnostic trouble
code check effectively then by carefully checking the results indicates how to proceed either to diagnostic
trouble code troubleshooting or to troubleshooting of problem s^mptoms
If a diagnostic trouble code was disminus
played in the initial diagnostic troublecode check it indicates that the troublemay have occurred in a wire harness orconnector in that circuit in the pastTherefore check the wire harness andconnectors (see page INminus24)
Troubleshooting of problemindicated by diagnostic trouminusble code
bull Normal code displayedbull Problem symptoms exist
bull Diagnostic trouble codedisplayed
bull Problem symptoms exist
Making a note of and clearing of thediagnostic trouble codes displayed
bull Normal code displayed
bull No problem symptomsexist
Simulation test using the symptomsimulation methods
No problem symptomsexist
Troubleshooting of eachproblem symptom
Symptom confirmation
Diagnostic trouble code check
Diagnostic trouble code check
Problem symptomsexist
System Normal
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The most difficult case in troubleshooting is when there are no problem symptoms occurring In such casesa thorough customer problem analysis must be carried out then simulate the same or similar conditions andenvironment in which the problem occurred in the customerrsquos vehicle No matter how much experience atechnician has or how skilled he may be if he proceeds to troubleshoot without confirming the problem
symptoms he will tend to overlook something important in the repair operation and make a wrong guesssomewhere which will only lead to a standstill For example for a problem which only occurs when theengine is cold or for a problem which occurs due to vibration caused by the road during driving etc theproblem can never be determined so long as the symptoms are confirmed with the engine hot condition orthe vehicle at a standstill Since vibration heat or water penetration (moisture) are likely causes for problemswhich are difficult to reproduce the symptom simulation tests introduced here are effective measures inthat the external causes are applied to the vehicle in a stopped conditionImportant Points in the Symptom Simulation TestIn the symptom simulation test the problem symptoms should of course be confirmed but the problem areaor parts must also be found out To do this narrow down the possible problem circuits according to thesymptoms before starting this test and connect a tester beforehand After that carry out the symptom simminus
ulation test judging whether the circuit being tested is defective or normal and also confirming the problem
symptoms at the same time Refer to the matrix chart of problem symptoms for each system to narrowdown the possible causes of the symptom
PARTS AND SENSORS
Apply slight vibration with a finger to the part of the senminus
sor considered to be the problem cause and check if the
malfunction occurs
HINT Applying strong vibration to relays may result
in open relays
WIRE HARNESS
Slightly shake the wire harness vertically and horizonminus
tally The connector joint fulcrum of the vibration and
body through portion are the major areas to be checked
thoroughly
CONNECTORS
Slightly shake the connector vertically and horizontally
VIBRATION METHOD When vibration seems to be the major cause
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The inspection procedure is shown in the table below This table permits efficient and accuratetroubleshooting using the diagnostic trouble codes displayed in the diagnostic trouble code check Proceedwith troubleshooting in accordance with the inspection procedure given in the diagnostic chart corresponminusding to the diagnostic trouble codes displayed
The engine diagnostic trouble code chart is shown below as an example
bull Page or InstructionsIndicates the page where the inspection prominuscedure for each circuit is to be found or gives inminus
structions for checking and repairs
bull Diagnostic Trouble CodeDetecting ConditionIndicates the diagnostic
trouble code setparameter
bull Detection ItemIndicates the system of the prominus
blem or contents of the problem
bull Trouble AreaIndicates the suspect area of the prominusblem
bull DTC NoIndicates the diagnostic troublecode
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The suspect circuits or parts for each problem symptom are shown in the table below Use this table totroubleshoot the problem when a rdquoNormalrdquo code is displayed in the diagnostic trouble code check but theproblem is still occurring Numbers in the table indicate the inspection order in which the circuits or partsshould be checkedHINT when the problem is not detected by the diagnostic system even though the problem symptom is
present it is considered that the problem is occurring outside the detection range of the diagnostic system
or that the problem is occurring in a system other than the diagnostic system
bull Circuit Inspection Inspection OrderIndicates the circuit which needs to be checked
for each problem symptom Check in the order inminus
dicated by the numbers
bull Circuit or Part NameIndicates the circuit or part which needs to bechecked
bull PageIndicates the page where the flow chart foreach circuit is located
bull Problem Symptom
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE1 For troubleshooting diagnostic trouble code charts or problem symptom charts are provided for each
circuit with detailed inspection procedures on the following pages
2 When all the component parts wire harnesses and connectors of each circuit except the ECU are
found to be normal in troubleshooting then it is determined that the problem is in the ECU
Accordingly if diagnosis is performed without the problem symptoms occurring the instruction will be
to check and replace the ECU even if the problem is not in the ECU So always confirm that the prominus
blem symptoms are occurring or proceed with inspection while using the symptom simulation
method
3 The instructions rdquoCheck wire harness and connectorrdquo and rdquoCheck and replace ECUrdquo which appear in
the inspection procedure are common and applicable to all diagnostic trouble codes Follow the prominus
cedure outlined below whenever these instructions appear
Check Wire Harness and ConnectorThe problem in the wire harness or connector is an open circuit or a short circuit
OPEN CIRCUITThis could be due to a disconnected wire harness faulty contact in the connector a connector terminal pullminus
ed out etc
HINT
1 It is rarely the case that a wire is broken in the middle of it Most cases occur at the connector In par minus
ticular carefully check the connectors of sensors and actuators
2 Faulty contact could be due to rusting of the connector terminals to foreign materials entering terminus
minals or a drop in the contact pressure between the male and female terminals of the connector Simpminus
ly disconnecting and reconnecting the connectors once changes the condition of the connection anc
may result in a return to normal operation
Therefore in troubleshooting if no abnormality is found in the wire harness and connector check but
the problem disappears after the check then the cause is considered to be in the wire harness or con
nectors
SHORT CIRCUITThis could be due to a short circuit between the wire harness and the body ground or to a short inside the
switch etc
HINT
bull When there is a short between the wire harness and body ground check thoroughly whether the wire
harness is caught in the body or is clamped properly
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
(1) Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connecminus
tor (A) and body ground
In the case of Fig 6
Between terminal 1 of connector (A) and body ground rarr Continuity
Between terminal 2 of connector (A) and body ground rarr No continuity (open)Therefore it is found out that there is a short circuit between terminal 1 of connector (A) and terminal
1 of connector (C)
(2) Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body
ground and terminal 1 of connector (B) and body ground
Between terminal 1 of connector (A) body ground rarr No continuity (open)
Between terminal 1 of connector (B) and body ground rarr Continuity
Therefore it is found out that there is a short circuit between terminal 1 of connector (B) and terminal
1 of connector (C)
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
In troubleshooting the problem symptoms must be confirmed accurately and all preconceptions must be
cleared away in order to give an accurate judgement To ascertain just what the problem symptoms are
it is extremely important to ask the customer about the problem and the conditions at the time it occurred
Important Points in the Problem Analysis
The following 5 items are important points in the problem analysis Past problems which are thought to beunrelated and the repair history etc may also help in some cases so as much information as possible shou
be gathered and its relationship with the problem symptoms should be correctly ascertained for reference
in troubleshooting A customer problem analysis table is provided in the troubleshooting section for each
system for your use
(Sample) Engine control system check sheet
Important Points in the Customer Problem Analysis
bull What Vehicle model system name
bull When Date time occurrence frequency
bull Where Road conditions
bull Under what conditions Running conditions driving conditions weather conditions
bull How did it happen Problem symptoms
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
In diagnostic trouble code check it is very important to determine whether the problem indicated by thediagnostic trouble code is still occurring or occurred in the past but returned to normal at present In addiminustion it must be checked in the problem symptom check whether the malfunction indicated by thediagnostic trouble code is directly related to the problem symptom or not For this reason the diagnostictrouble codes should be checked before and after the symptom confirmation to determine the current condtions as shown in the table below If this is not done it may depending on the case result in unnecessarytroubleshooting for normally operating systems thus making it more difficult to locate the problem or inrepairs not pertinent to the problem Therefore always follow the procedure in correct order and performthe diagnostic trouble code checkDIAGNOSTIC TROUBLE CODE CHECK PROCEDURE
2 SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE CHECK
The diagnostic system in the TACOMA fulfills various functions The first function is the Diagnostic Trouble
Code Check in which a malfunction in the signal circuits to the ECU is stored in code in the ECU memory at
the time of occurrence to be output by the technician during troubleshooting Another function is the Input
Signal Check which checks if the signals from various switches are sent to the ECU correctly The air condiminus
tioner system has an Actuator Check function whereby the ECU automatically operates the actuators of thedamper and blowermotor etc to check the operation By using these check functions the problem areas
can be narrowed down quickly and troubleshooting can be performed effectively Diagnostic functions are
incorporated in the following systems in the TACOMA
The problem is still occurring in a place otherthan in the diagnostic circuit(The diagnostic trouble code displayed first iseither for a past problem or it is a secondaryproblem)
The problem is still occurring in a place otherthan in the diagnostic circuit
The problem occurred in a place other than inthe diagnostic circuit in the past
The problem occurred in the diagnostic circuitin the past
Problem is still occurring in the diagnosticcircuit
Diagnostic TroubleCode Check (Make anote of and thenclear)
Supplemental Restraint System
Same diagnostictrouble code isdisplayed
Normal code isdisplayed
Other DiagnosisFunction
Input Signal Check(Sensor Check)
Diagnostic TroubleCode Check
Diagnostic TroubleCode Check
Problem Condition
Diagnostic TroubleCode Display
No problemsymptoms exist
Confirmation ofSymptoms
Problem symptomsexist
Problem symptomsexist
Normal code isdisplayed
No problemsymptoms exist
Normal code isdisplayed
Automatic Transmission O (with Check Mode)
O (with Check Mode)
O (with Check Mode)
Diagnostic Test Mode
Diagnostic Test Mode
Diagnostic Test Mode
Normal Code Display
2RZminusFE 3RZminusFE
System
Engine
5VZminusFE
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
Taking into account the above points a flow chart showing how to proceed with troubleshooting using the
diagnostic trouble code check is shown below This flow chart shows how to utilize the diagnostic trouble
code check effectively then by carefully checking the results indicates how to proceed either to diagnostic
trouble code troubleshooting or to troubleshooting of problem s^mptoms
If a diagnostic trouble code was disminus
played in the initial diagnostic troublecode check it indicates that the troublemay have occurred in a wire harness orconnector in that circuit in the pastTherefore check the wire harness andconnectors (see page INminus24)
Troubleshooting of problemindicated by diagnostic trouminusble code
bull Normal code displayedbull Problem symptoms exist
bull Diagnostic trouble codedisplayed
bull Problem symptoms exist
Making a note of and clearing of thediagnostic trouble codes displayed
bull Normal code displayed
bull No problem symptomsexist
Simulation test using the symptomsimulation methods
No problem symptomsexist
Troubleshooting of eachproblem symptom
Symptom confirmation
Diagnostic trouble code check
Diagnostic trouble code check
Problem symptomsexist
System Normal
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The most difficult case in troubleshooting is when there are no problem symptoms occurring In such casesa thorough customer problem analysis must be carried out then simulate the same or similar conditions andenvironment in which the problem occurred in the customerrsquos vehicle No matter how much experience atechnician has or how skilled he may be if he proceeds to troubleshoot without confirming the problem
symptoms he will tend to overlook something important in the repair operation and make a wrong guesssomewhere which will only lead to a standstill For example for a problem which only occurs when theengine is cold or for a problem which occurs due to vibration caused by the road during driving etc theproblem can never be determined so long as the symptoms are confirmed with the engine hot condition orthe vehicle at a standstill Since vibration heat or water penetration (moisture) are likely causes for problemswhich are difficult to reproduce the symptom simulation tests introduced here are effective measures inthat the external causes are applied to the vehicle in a stopped conditionImportant Points in the Symptom Simulation TestIn the symptom simulation test the problem symptoms should of course be confirmed but the problem areaor parts must also be found out To do this narrow down the possible problem circuits according to thesymptoms before starting this test and connect a tester beforehand After that carry out the symptom simminus
ulation test judging whether the circuit being tested is defective or normal and also confirming the problem
symptoms at the same time Refer to the matrix chart of problem symptoms for each system to narrowdown the possible causes of the symptom
PARTS AND SENSORS
Apply slight vibration with a finger to the part of the senminus
sor considered to be the problem cause and check if the
malfunction occurs
HINT Applying strong vibration to relays may result
in open relays
WIRE HARNESS
Slightly shake the wire harness vertically and horizonminus
tally The connector joint fulcrum of the vibration and
body through portion are the major areas to be checked
thoroughly
CONNECTORS
Slightly shake the connector vertically and horizontally
VIBRATION METHOD When vibration seems to be the major cause
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The inspection procedure is shown in the table below This table permits efficient and accuratetroubleshooting using the diagnostic trouble codes displayed in the diagnostic trouble code check Proceedwith troubleshooting in accordance with the inspection procedure given in the diagnostic chart corresponminusding to the diagnostic trouble codes displayed
The engine diagnostic trouble code chart is shown below as an example
bull Page or InstructionsIndicates the page where the inspection prominuscedure for each circuit is to be found or gives inminus
structions for checking and repairs
bull Diagnostic Trouble CodeDetecting ConditionIndicates the diagnostic
trouble code setparameter
bull Detection ItemIndicates the system of the prominus
blem or contents of the problem
bull Trouble AreaIndicates the suspect area of the prominusblem
bull DTC NoIndicates the diagnostic troublecode
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The suspect circuits or parts for each problem symptom are shown in the table below Use this table totroubleshoot the problem when a rdquoNormalrdquo code is displayed in the diagnostic trouble code check but theproblem is still occurring Numbers in the table indicate the inspection order in which the circuits or partsshould be checkedHINT when the problem is not detected by the diagnostic system even though the problem symptom is
present it is considered that the problem is occurring outside the detection range of the diagnostic system
or that the problem is occurring in a system other than the diagnostic system
bull Circuit Inspection Inspection OrderIndicates the circuit which needs to be checked
for each problem symptom Check in the order inminus
dicated by the numbers
bull Circuit or Part NameIndicates the circuit or part which needs to bechecked
bull PageIndicates the page where the flow chart foreach circuit is located
bull Problem Symptom
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE1 For troubleshooting diagnostic trouble code charts or problem symptom charts are provided for each
circuit with detailed inspection procedures on the following pages
2 When all the component parts wire harnesses and connectors of each circuit except the ECU are
found to be normal in troubleshooting then it is determined that the problem is in the ECU
Accordingly if diagnosis is performed without the problem symptoms occurring the instruction will be
to check and replace the ECU even if the problem is not in the ECU So always confirm that the prominus
blem symptoms are occurring or proceed with inspection while using the symptom simulation
method
3 The instructions rdquoCheck wire harness and connectorrdquo and rdquoCheck and replace ECUrdquo which appear in
the inspection procedure are common and applicable to all diagnostic trouble codes Follow the prominus
cedure outlined below whenever these instructions appear
Check Wire Harness and ConnectorThe problem in the wire harness or connector is an open circuit or a short circuit
OPEN CIRCUITThis could be due to a disconnected wire harness faulty contact in the connector a connector terminal pullminus
ed out etc
HINT
1 It is rarely the case that a wire is broken in the middle of it Most cases occur at the connector In par minus
ticular carefully check the connectors of sensors and actuators
2 Faulty contact could be due to rusting of the connector terminals to foreign materials entering terminus
minals or a drop in the contact pressure between the male and female terminals of the connector Simpminus
ly disconnecting and reconnecting the connectors once changes the condition of the connection anc
may result in a return to normal operation
Therefore in troubleshooting if no abnormality is found in the wire harness and connector check but
the problem disappears after the check then the cause is considered to be in the wire harness or con
nectors
SHORT CIRCUITThis could be due to a short circuit between the wire harness and the body ground or to a short inside the
switch etc
HINT
bull When there is a short between the wire harness and body ground check thoroughly whether the wire
harness is caught in the body or is clamped properly
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
(1) Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connecminus
tor (A) and body ground
In the case of Fig 6
Between terminal 1 of connector (A) and body ground rarr Continuity
Between terminal 2 of connector (A) and body ground rarr No continuity (open)Therefore it is found out that there is a short circuit between terminal 1 of connector (A) and terminal
1 of connector (C)
(2) Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body
ground and terminal 1 of connector (B) and body ground
Between terminal 1 of connector (A) body ground rarr No continuity (open)
Between terminal 1 of connector (B) and body ground rarr Continuity
Therefore it is found out that there is a short circuit between terminal 1 of connector (B) and terminal
1 of connector (C)
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
In diagnostic trouble code check it is very important to determine whether the problem indicated by thediagnostic trouble code is still occurring or occurred in the past but returned to normal at present In addiminustion it must be checked in the problem symptom check whether the malfunction indicated by thediagnostic trouble code is directly related to the problem symptom or not For this reason the diagnostictrouble codes should be checked before and after the symptom confirmation to determine the current condtions as shown in the table below If this is not done it may depending on the case result in unnecessarytroubleshooting for normally operating systems thus making it more difficult to locate the problem or inrepairs not pertinent to the problem Therefore always follow the procedure in correct order and performthe diagnostic trouble code checkDIAGNOSTIC TROUBLE CODE CHECK PROCEDURE
2 SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE CHECK
The diagnostic system in the TACOMA fulfills various functions The first function is the Diagnostic Trouble
Code Check in which a malfunction in the signal circuits to the ECU is stored in code in the ECU memory at
the time of occurrence to be output by the technician during troubleshooting Another function is the Input
Signal Check which checks if the signals from various switches are sent to the ECU correctly The air condiminus
tioner system has an Actuator Check function whereby the ECU automatically operates the actuators of thedamper and blowermotor etc to check the operation By using these check functions the problem areas
can be narrowed down quickly and troubleshooting can be performed effectively Diagnostic functions are
incorporated in the following systems in the TACOMA
The problem is still occurring in a place otherthan in the diagnostic circuit(The diagnostic trouble code displayed first iseither for a past problem or it is a secondaryproblem)
The problem is still occurring in a place otherthan in the diagnostic circuit
The problem occurred in a place other than inthe diagnostic circuit in the past
The problem occurred in the diagnostic circuitin the past
Problem is still occurring in the diagnosticcircuit
Diagnostic TroubleCode Check (Make anote of and thenclear)
Supplemental Restraint System
Same diagnostictrouble code isdisplayed
Normal code isdisplayed
Other DiagnosisFunction
Input Signal Check(Sensor Check)
Diagnostic TroubleCode Check
Diagnostic TroubleCode Check
Problem Condition
Diagnostic TroubleCode Display
No problemsymptoms exist
Confirmation ofSymptoms
Problem symptomsexist
Problem symptomsexist
Normal code isdisplayed
No problemsymptoms exist
Normal code isdisplayed
Automatic Transmission O (with Check Mode)
O (with Check Mode)
O (with Check Mode)
Diagnostic Test Mode
Diagnostic Test Mode
Diagnostic Test Mode
Normal Code Display
2RZminusFE 3RZminusFE
System
Engine
5VZminusFE
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
Taking into account the above points a flow chart showing how to proceed with troubleshooting using the
diagnostic trouble code check is shown below This flow chart shows how to utilize the diagnostic trouble
code check effectively then by carefully checking the results indicates how to proceed either to diagnostic
trouble code troubleshooting or to troubleshooting of problem s^mptoms
If a diagnostic trouble code was disminus
played in the initial diagnostic troublecode check it indicates that the troublemay have occurred in a wire harness orconnector in that circuit in the pastTherefore check the wire harness andconnectors (see page INminus24)
Troubleshooting of problemindicated by diagnostic trouminusble code
bull Normal code displayedbull Problem symptoms exist
bull Diagnostic trouble codedisplayed
bull Problem symptoms exist
Making a note of and clearing of thediagnostic trouble codes displayed
bull Normal code displayed
bull No problem symptomsexist
Simulation test using the symptomsimulation methods
No problem symptomsexist
Troubleshooting of eachproblem symptom
Symptom confirmation
Diagnostic trouble code check
Diagnostic trouble code check
Problem symptomsexist
System Normal
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The most difficult case in troubleshooting is when there are no problem symptoms occurring In such casesa thorough customer problem analysis must be carried out then simulate the same or similar conditions andenvironment in which the problem occurred in the customerrsquos vehicle No matter how much experience atechnician has or how skilled he may be if he proceeds to troubleshoot without confirming the problem
symptoms he will tend to overlook something important in the repair operation and make a wrong guesssomewhere which will only lead to a standstill For example for a problem which only occurs when theengine is cold or for a problem which occurs due to vibration caused by the road during driving etc theproblem can never be determined so long as the symptoms are confirmed with the engine hot condition orthe vehicle at a standstill Since vibration heat or water penetration (moisture) are likely causes for problemswhich are difficult to reproduce the symptom simulation tests introduced here are effective measures inthat the external causes are applied to the vehicle in a stopped conditionImportant Points in the Symptom Simulation TestIn the symptom simulation test the problem symptoms should of course be confirmed but the problem areaor parts must also be found out To do this narrow down the possible problem circuits according to thesymptoms before starting this test and connect a tester beforehand After that carry out the symptom simminus
ulation test judging whether the circuit being tested is defective or normal and also confirming the problem
symptoms at the same time Refer to the matrix chart of problem symptoms for each system to narrowdown the possible causes of the symptom
PARTS AND SENSORS
Apply slight vibration with a finger to the part of the senminus
sor considered to be the problem cause and check if the
malfunction occurs
HINT Applying strong vibration to relays may result
in open relays
WIRE HARNESS
Slightly shake the wire harness vertically and horizonminus
tally The connector joint fulcrum of the vibration and
body through portion are the major areas to be checked
thoroughly
CONNECTORS
Slightly shake the connector vertically and horizontally
VIBRATION METHOD When vibration seems to be the major cause
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The inspection procedure is shown in the table below This table permits efficient and accuratetroubleshooting using the diagnostic trouble codes displayed in the diagnostic trouble code check Proceedwith troubleshooting in accordance with the inspection procedure given in the diagnostic chart corresponminusding to the diagnostic trouble codes displayed
The engine diagnostic trouble code chart is shown below as an example
bull Page or InstructionsIndicates the page where the inspection prominuscedure for each circuit is to be found or gives inminus
structions for checking and repairs
bull Diagnostic Trouble CodeDetecting ConditionIndicates the diagnostic
trouble code setparameter
bull Detection ItemIndicates the system of the prominus
blem or contents of the problem
bull Trouble AreaIndicates the suspect area of the prominusblem
bull DTC NoIndicates the diagnostic troublecode
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The suspect circuits or parts for each problem symptom are shown in the table below Use this table totroubleshoot the problem when a rdquoNormalrdquo code is displayed in the diagnostic trouble code check but theproblem is still occurring Numbers in the table indicate the inspection order in which the circuits or partsshould be checkedHINT when the problem is not detected by the diagnostic system even though the problem symptom is
present it is considered that the problem is occurring outside the detection range of the diagnostic system
or that the problem is occurring in a system other than the diagnostic system
bull Circuit Inspection Inspection OrderIndicates the circuit which needs to be checked
for each problem symptom Check in the order inminus
dicated by the numbers
bull Circuit or Part NameIndicates the circuit or part which needs to bechecked
bull PageIndicates the page where the flow chart foreach circuit is located
bull Problem Symptom
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE1 For troubleshooting diagnostic trouble code charts or problem symptom charts are provided for each
circuit with detailed inspection procedures on the following pages
2 When all the component parts wire harnesses and connectors of each circuit except the ECU are
found to be normal in troubleshooting then it is determined that the problem is in the ECU
Accordingly if diagnosis is performed without the problem symptoms occurring the instruction will be
to check and replace the ECU even if the problem is not in the ECU So always confirm that the prominus
blem symptoms are occurring or proceed with inspection while using the symptom simulation
method
3 The instructions rdquoCheck wire harness and connectorrdquo and rdquoCheck and replace ECUrdquo which appear in
the inspection procedure are common and applicable to all diagnostic trouble codes Follow the prominus
cedure outlined below whenever these instructions appear
Check Wire Harness and ConnectorThe problem in the wire harness or connector is an open circuit or a short circuit
OPEN CIRCUITThis could be due to a disconnected wire harness faulty contact in the connector a connector terminal pullminus
ed out etc
HINT
1 It is rarely the case that a wire is broken in the middle of it Most cases occur at the connector In par minus
ticular carefully check the connectors of sensors and actuators
2 Faulty contact could be due to rusting of the connector terminals to foreign materials entering terminus
minals or a drop in the contact pressure between the male and female terminals of the connector Simpminus
ly disconnecting and reconnecting the connectors once changes the condition of the connection anc
may result in a return to normal operation
Therefore in troubleshooting if no abnormality is found in the wire harness and connector check but
the problem disappears after the check then the cause is considered to be in the wire harness or con
nectors
SHORT CIRCUITThis could be due to a short circuit between the wire harness and the body ground or to a short inside the
switch etc
HINT
bull When there is a short between the wire harness and body ground check thoroughly whether the wire
harness is caught in the body or is clamped properly
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
(1) Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connecminus
tor (A) and body ground
In the case of Fig 6
Between terminal 1 of connector (A) and body ground rarr Continuity
Between terminal 2 of connector (A) and body ground rarr No continuity (open)Therefore it is found out that there is a short circuit between terminal 1 of connector (A) and terminal
1 of connector (C)
(2) Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body
ground and terminal 1 of connector (B) and body ground
Between terminal 1 of connector (A) body ground rarr No continuity (open)
Between terminal 1 of connector (B) and body ground rarr Continuity
Therefore it is found out that there is a short circuit between terminal 1 of connector (B) and terminal
1 of connector (C)
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
Taking into account the above points a flow chart showing how to proceed with troubleshooting using the
diagnostic trouble code check is shown below This flow chart shows how to utilize the diagnostic trouble
code check effectively then by carefully checking the results indicates how to proceed either to diagnostic
trouble code troubleshooting or to troubleshooting of problem s^mptoms
If a diagnostic trouble code was disminus
played in the initial diagnostic troublecode check it indicates that the troublemay have occurred in a wire harness orconnector in that circuit in the pastTherefore check the wire harness andconnectors (see page INminus24)
Troubleshooting of problemindicated by diagnostic trouminusble code
bull Normal code displayedbull Problem symptoms exist
bull Diagnostic trouble codedisplayed
bull Problem symptoms exist
Making a note of and clearing of thediagnostic trouble codes displayed
bull Normal code displayed
bull No problem symptomsexist
Simulation test using the symptomsimulation methods
No problem symptomsexist
Troubleshooting of eachproblem symptom
Symptom confirmation
Diagnostic trouble code check
Diagnostic trouble code check
Problem symptomsexist
System Normal
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The most difficult case in troubleshooting is when there are no problem symptoms occurring In such casesa thorough customer problem analysis must be carried out then simulate the same or similar conditions andenvironment in which the problem occurred in the customerrsquos vehicle No matter how much experience atechnician has or how skilled he may be if he proceeds to troubleshoot without confirming the problem
symptoms he will tend to overlook something important in the repair operation and make a wrong guesssomewhere which will only lead to a standstill For example for a problem which only occurs when theengine is cold or for a problem which occurs due to vibration caused by the road during driving etc theproblem can never be determined so long as the symptoms are confirmed with the engine hot condition orthe vehicle at a standstill Since vibration heat or water penetration (moisture) are likely causes for problemswhich are difficult to reproduce the symptom simulation tests introduced here are effective measures inthat the external causes are applied to the vehicle in a stopped conditionImportant Points in the Symptom Simulation TestIn the symptom simulation test the problem symptoms should of course be confirmed but the problem areaor parts must also be found out To do this narrow down the possible problem circuits according to thesymptoms before starting this test and connect a tester beforehand After that carry out the symptom simminus
ulation test judging whether the circuit being tested is defective or normal and also confirming the problem
symptoms at the same time Refer to the matrix chart of problem symptoms for each system to narrowdown the possible causes of the symptom
PARTS AND SENSORS
Apply slight vibration with a finger to the part of the senminus
sor considered to be the problem cause and check if the
malfunction occurs
HINT Applying strong vibration to relays may result
in open relays
WIRE HARNESS
Slightly shake the wire harness vertically and horizonminus
tally The connector joint fulcrum of the vibration and
body through portion are the major areas to be checked
thoroughly
CONNECTORS
Slightly shake the connector vertically and horizontally
VIBRATION METHOD When vibration seems to be the major cause
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The inspection procedure is shown in the table below This table permits efficient and accuratetroubleshooting using the diagnostic trouble codes displayed in the diagnostic trouble code check Proceedwith troubleshooting in accordance with the inspection procedure given in the diagnostic chart corresponminusding to the diagnostic trouble codes displayed
The engine diagnostic trouble code chart is shown below as an example
bull Page or InstructionsIndicates the page where the inspection prominuscedure for each circuit is to be found or gives inminus
structions for checking and repairs
bull Diagnostic Trouble CodeDetecting ConditionIndicates the diagnostic
trouble code setparameter
bull Detection ItemIndicates the system of the prominus
blem or contents of the problem
bull Trouble AreaIndicates the suspect area of the prominusblem
bull DTC NoIndicates the diagnostic troublecode
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The suspect circuits or parts for each problem symptom are shown in the table below Use this table totroubleshoot the problem when a rdquoNormalrdquo code is displayed in the diagnostic trouble code check but theproblem is still occurring Numbers in the table indicate the inspection order in which the circuits or partsshould be checkedHINT when the problem is not detected by the diagnostic system even though the problem symptom is
present it is considered that the problem is occurring outside the detection range of the diagnostic system
or that the problem is occurring in a system other than the diagnostic system
bull Circuit Inspection Inspection OrderIndicates the circuit which needs to be checked
for each problem symptom Check in the order inminus
dicated by the numbers
bull Circuit or Part NameIndicates the circuit or part which needs to bechecked
bull PageIndicates the page where the flow chart foreach circuit is located
bull Problem Symptom
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE1 For troubleshooting diagnostic trouble code charts or problem symptom charts are provided for each
circuit with detailed inspection procedures on the following pages
2 When all the component parts wire harnesses and connectors of each circuit except the ECU are
found to be normal in troubleshooting then it is determined that the problem is in the ECU
Accordingly if diagnosis is performed without the problem symptoms occurring the instruction will be
to check and replace the ECU even if the problem is not in the ECU So always confirm that the prominus
blem symptoms are occurring or proceed with inspection while using the symptom simulation
method
3 The instructions rdquoCheck wire harness and connectorrdquo and rdquoCheck and replace ECUrdquo which appear in
the inspection procedure are common and applicable to all diagnostic trouble codes Follow the prominus
cedure outlined below whenever these instructions appear
Check Wire Harness and ConnectorThe problem in the wire harness or connector is an open circuit or a short circuit
OPEN CIRCUITThis could be due to a disconnected wire harness faulty contact in the connector a connector terminal pullminus
ed out etc
HINT
1 It is rarely the case that a wire is broken in the middle of it Most cases occur at the connector In par minus
ticular carefully check the connectors of sensors and actuators
2 Faulty contact could be due to rusting of the connector terminals to foreign materials entering terminus
minals or a drop in the contact pressure between the male and female terminals of the connector Simpminus
ly disconnecting and reconnecting the connectors once changes the condition of the connection anc
may result in a return to normal operation
Therefore in troubleshooting if no abnormality is found in the wire harness and connector check but
the problem disappears after the check then the cause is considered to be in the wire harness or con
nectors
SHORT CIRCUITThis could be due to a short circuit between the wire harness and the body ground or to a short inside the
switch etc
HINT
bull When there is a short between the wire harness and body ground check thoroughly whether the wire
harness is caught in the body or is clamped properly
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
(1) Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connecminus
tor (A) and body ground
In the case of Fig 6
Between terminal 1 of connector (A) and body ground rarr Continuity
Between terminal 2 of connector (A) and body ground rarr No continuity (open)Therefore it is found out that there is a short circuit between terminal 1 of connector (A) and terminal
1 of connector (C)
(2) Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body
ground and terminal 1 of connector (B) and body ground
Between terminal 1 of connector (A) body ground rarr No continuity (open)
Between terminal 1 of connector (B) and body ground rarr Continuity
Therefore it is found out that there is a short circuit between terminal 1 of connector (B) and terminal
1 of connector (C)
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The most difficult case in troubleshooting is when there are no problem symptoms occurring In such casesa thorough customer problem analysis must be carried out then simulate the same or similar conditions andenvironment in which the problem occurred in the customerrsquos vehicle No matter how much experience atechnician has or how skilled he may be if he proceeds to troubleshoot without confirming the problem
symptoms he will tend to overlook something important in the repair operation and make a wrong guesssomewhere which will only lead to a standstill For example for a problem which only occurs when theengine is cold or for a problem which occurs due to vibration caused by the road during driving etc theproblem can never be determined so long as the symptoms are confirmed with the engine hot condition orthe vehicle at a standstill Since vibration heat or water penetration (moisture) are likely causes for problemswhich are difficult to reproduce the symptom simulation tests introduced here are effective measures inthat the external causes are applied to the vehicle in a stopped conditionImportant Points in the Symptom Simulation TestIn the symptom simulation test the problem symptoms should of course be confirmed but the problem areaor parts must also be found out To do this narrow down the possible problem circuits according to thesymptoms before starting this test and connect a tester beforehand After that carry out the symptom simminus
ulation test judging whether the circuit being tested is defective or normal and also confirming the problem
symptoms at the same time Refer to the matrix chart of problem symptoms for each system to narrowdown the possible causes of the symptom
PARTS AND SENSORS
Apply slight vibration with a finger to the part of the senminus
sor considered to be the problem cause and check if the
malfunction occurs
HINT Applying strong vibration to relays may result
in open relays
WIRE HARNESS
Slightly shake the wire harness vertically and horizonminus
tally The connector joint fulcrum of the vibration and
body through portion are the major areas to be checked
thoroughly
CONNECTORS
Slightly shake the connector vertically and horizontally
VIBRATION METHOD When vibration seems to be the major cause
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The inspection procedure is shown in the table below This table permits efficient and accuratetroubleshooting using the diagnostic trouble codes displayed in the diagnostic trouble code check Proceedwith troubleshooting in accordance with the inspection procedure given in the diagnostic chart corresponminusding to the diagnostic trouble codes displayed
The engine diagnostic trouble code chart is shown below as an example
bull Page or InstructionsIndicates the page where the inspection prominuscedure for each circuit is to be found or gives inminus
structions for checking and repairs
bull Diagnostic Trouble CodeDetecting ConditionIndicates the diagnostic
trouble code setparameter
bull Detection ItemIndicates the system of the prominus
blem or contents of the problem
bull Trouble AreaIndicates the suspect area of the prominusblem
bull DTC NoIndicates the diagnostic troublecode
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The suspect circuits or parts for each problem symptom are shown in the table below Use this table totroubleshoot the problem when a rdquoNormalrdquo code is displayed in the diagnostic trouble code check but theproblem is still occurring Numbers in the table indicate the inspection order in which the circuits or partsshould be checkedHINT when the problem is not detected by the diagnostic system even though the problem symptom is
present it is considered that the problem is occurring outside the detection range of the diagnostic system
or that the problem is occurring in a system other than the diagnostic system
bull Circuit Inspection Inspection OrderIndicates the circuit which needs to be checked
for each problem symptom Check in the order inminus
dicated by the numbers
bull Circuit or Part NameIndicates the circuit or part which needs to bechecked
bull PageIndicates the page where the flow chart foreach circuit is located
bull Problem Symptom
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE1 For troubleshooting diagnostic trouble code charts or problem symptom charts are provided for each
circuit with detailed inspection procedures on the following pages
2 When all the component parts wire harnesses and connectors of each circuit except the ECU are
found to be normal in troubleshooting then it is determined that the problem is in the ECU
Accordingly if diagnosis is performed without the problem symptoms occurring the instruction will be
to check and replace the ECU even if the problem is not in the ECU So always confirm that the prominus
blem symptoms are occurring or proceed with inspection while using the symptom simulation
method
3 The instructions rdquoCheck wire harness and connectorrdquo and rdquoCheck and replace ECUrdquo which appear in
the inspection procedure are common and applicable to all diagnostic trouble codes Follow the prominus
cedure outlined below whenever these instructions appear
Check Wire Harness and ConnectorThe problem in the wire harness or connector is an open circuit or a short circuit
OPEN CIRCUITThis could be due to a disconnected wire harness faulty contact in the connector a connector terminal pullminus
ed out etc
HINT
1 It is rarely the case that a wire is broken in the middle of it Most cases occur at the connector In par minus
ticular carefully check the connectors of sensors and actuators
2 Faulty contact could be due to rusting of the connector terminals to foreign materials entering terminus
minals or a drop in the contact pressure between the male and female terminals of the connector Simpminus
ly disconnecting and reconnecting the connectors once changes the condition of the connection anc
may result in a return to normal operation
Therefore in troubleshooting if no abnormality is found in the wire harness and connector check but
the problem disappears after the check then the cause is considered to be in the wire harness or con
nectors
SHORT CIRCUITThis could be due to a short circuit between the wire harness and the body ground or to a short inside the
switch etc
HINT
bull When there is a short between the wire harness and body ground check thoroughly whether the wire
harness is caught in the body or is clamped properly
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
(1) Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connecminus
tor (A) and body ground
In the case of Fig 6
Between terminal 1 of connector (A) and body ground rarr Continuity
Between terminal 2 of connector (A) and body ground rarr No continuity (open)Therefore it is found out that there is a short circuit between terminal 1 of connector (A) and terminal
1 of connector (C)
(2) Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body
ground and terminal 1 of connector (B) and body ground
Between terminal 1 of connector (A) body ground rarr No continuity (open)
Between terminal 1 of connector (B) and body ground rarr Continuity
Therefore it is found out that there is a short circuit between terminal 1 of connector (B) and terminal
1 of connector (C)
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The inspection procedure is shown in the table below This table permits efficient and accuratetroubleshooting using the diagnostic trouble codes displayed in the diagnostic trouble code check Proceedwith troubleshooting in accordance with the inspection procedure given in the diagnostic chart corresponminusding to the diagnostic trouble codes displayed
The engine diagnostic trouble code chart is shown below as an example
bull Page or InstructionsIndicates the page where the inspection prominuscedure for each circuit is to be found or gives inminus
structions for checking and repairs
bull Diagnostic Trouble CodeDetecting ConditionIndicates the diagnostic
trouble code setparameter
bull Detection ItemIndicates the system of the prominus
blem or contents of the problem
bull Trouble AreaIndicates the suspect area of the prominusblem
bull DTC NoIndicates the diagnostic troublecode
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The suspect circuits or parts for each problem symptom are shown in the table below Use this table totroubleshoot the problem when a rdquoNormalrdquo code is displayed in the diagnostic trouble code check but theproblem is still occurring Numbers in the table indicate the inspection order in which the circuits or partsshould be checkedHINT when the problem is not detected by the diagnostic system even though the problem symptom is
present it is considered that the problem is occurring outside the detection range of the diagnostic system
or that the problem is occurring in a system other than the diagnostic system
bull Circuit Inspection Inspection OrderIndicates the circuit which needs to be checked
for each problem symptom Check in the order inminus
dicated by the numbers
bull Circuit or Part NameIndicates the circuit or part which needs to bechecked
bull PageIndicates the page where the flow chart foreach circuit is located
bull Problem Symptom
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE1 For troubleshooting diagnostic trouble code charts or problem symptom charts are provided for each
circuit with detailed inspection procedures on the following pages
2 When all the component parts wire harnesses and connectors of each circuit except the ECU are
found to be normal in troubleshooting then it is determined that the problem is in the ECU
Accordingly if diagnosis is performed without the problem symptoms occurring the instruction will be
to check and replace the ECU even if the problem is not in the ECU So always confirm that the prominus
blem symptoms are occurring or proceed with inspection while using the symptom simulation
method
3 The instructions rdquoCheck wire harness and connectorrdquo and rdquoCheck and replace ECUrdquo which appear in
the inspection procedure are common and applicable to all diagnostic trouble codes Follow the prominus
cedure outlined below whenever these instructions appear
Check Wire Harness and ConnectorThe problem in the wire harness or connector is an open circuit or a short circuit
OPEN CIRCUITThis could be due to a disconnected wire harness faulty contact in the connector a connector terminal pullminus
ed out etc
HINT
1 It is rarely the case that a wire is broken in the middle of it Most cases occur at the connector In par minus
ticular carefully check the connectors of sensors and actuators
2 Faulty contact could be due to rusting of the connector terminals to foreign materials entering terminus
minals or a drop in the contact pressure between the male and female terminals of the connector Simpminus
ly disconnecting and reconnecting the connectors once changes the condition of the connection anc
may result in a return to normal operation
Therefore in troubleshooting if no abnormality is found in the wire harness and connector check but
the problem disappears after the check then the cause is considered to be in the wire harness or con
nectors
SHORT CIRCUITThis could be due to a short circuit between the wire harness and the body ground or to a short inside the
switch etc
HINT
bull When there is a short between the wire harness and body ground check thoroughly whether the wire
harness is caught in the body or is clamped properly
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
(1) Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connecminus
tor (A) and body ground
In the case of Fig 6
Between terminal 1 of connector (A) and body ground rarr Continuity
Between terminal 2 of connector (A) and body ground rarr No continuity (open)Therefore it is found out that there is a short circuit between terminal 1 of connector (A) and terminal
1 of connector (C)
(2) Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body
ground and terminal 1 of connector (B) and body ground
Between terminal 1 of connector (A) body ground rarr No continuity (open)
Between terminal 1 of connector (B) and body ground rarr Continuity
Therefore it is found out that there is a short circuit between terminal 1 of connector (B) and terminal
1 of connector (C)
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The inspection procedure is shown in the table below This table permits efficient and accuratetroubleshooting using the diagnostic trouble codes displayed in the diagnostic trouble code check Proceedwith troubleshooting in accordance with the inspection procedure given in the diagnostic chart corresponminusding to the diagnostic trouble codes displayed
The engine diagnostic trouble code chart is shown below as an example
bull Page or InstructionsIndicates the page where the inspection prominuscedure for each circuit is to be found or gives inminus
structions for checking and repairs
bull Diagnostic Trouble CodeDetecting ConditionIndicates the diagnostic
trouble code setparameter
bull Detection ItemIndicates the system of the prominus
blem or contents of the problem
bull Trouble AreaIndicates the suspect area of the prominusblem
bull DTC NoIndicates the diagnostic troublecode
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The suspect circuits or parts for each problem symptom are shown in the table below Use this table totroubleshoot the problem when a rdquoNormalrdquo code is displayed in the diagnostic trouble code check but theproblem is still occurring Numbers in the table indicate the inspection order in which the circuits or partsshould be checkedHINT when the problem is not detected by the diagnostic system even though the problem symptom is
present it is considered that the problem is occurring outside the detection range of the diagnostic system
or that the problem is occurring in a system other than the diagnostic system
bull Circuit Inspection Inspection OrderIndicates the circuit which needs to be checked
for each problem symptom Check in the order inminus
dicated by the numbers
bull Circuit or Part NameIndicates the circuit or part which needs to bechecked
bull PageIndicates the page where the flow chart foreach circuit is located
bull Problem Symptom
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE1 For troubleshooting diagnostic trouble code charts or problem symptom charts are provided for each
circuit with detailed inspection procedures on the following pages
2 When all the component parts wire harnesses and connectors of each circuit except the ECU are
found to be normal in troubleshooting then it is determined that the problem is in the ECU
Accordingly if diagnosis is performed without the problem symptoms occurring the instruction will be
to check and replace the ECU even if the problem is not in the ECU So always confirm that the prominus
blem symptoms are occurring or proceed with inspection while using the symptom simulation
method
3 The instructions rdquoCheck wire harness and connectorrdquo and rdquoCheck and replace ECUrdquo which appear in
the inspection procedure are common and applicable to all diagnostic trouble codes Follow the prominus
cedure outlined below whenever these instructions appear
Check Wire Harness and ConnectorThe problem in the wire harness or connector is an open circuit or a short circuit
OPEN CIRCUITThis could be due to a disconnected wire harness faulty contact in the connector a connector terminal pullminus
ed out etc
HINT
1 It is rarely the case that a wire is broken in the middle of it Most cases occur at the connector In par minus
ticular carefully check the connectors of sensors and actuators
2 Faulty contact could be due to rusting of the connector terminals to foreign materials entering terminus
minals or a drop in the contact pressure between the male and female terminals of the connector Simpminus
ly disconnecting and reconnecting the connectors once changes the condition of the connection anc
may result in a return to normal operation
Therefore in troubleshooting if no abnormality is found in the wire harness and connector check but
the problem disappears after the check then the cause is considered to be in the wire harness or con
nectors
SHORT CIRCUITThis could be due to a short circuit between the wire harness and the body ground or to a short inside the
switch etc
HINT
bull When there is a short between the wire harness and body ground check thoroughly whether the wire
harness is caught in the body or is clamped properly
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
(1) Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connecminus
tor (A) and body ground
In the case of Fig 6
Between terminal 1 of connector (A) and body ground rarr Continuity
Between terminal 2 of connector (A) and body ground rarr No continuity (open)Therefore it is found out that there is a short circuit between terminal 1 of connector (A) and terminal
1 of connector (C)
(2) Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body
ground and terminal 1 of connector (B) and body ground
Between terminal 1 of connector (A) body ground rarr No continuity (open)
Between terminal 1 of connector (B) and body ground rarr Continuity
Therefore it is found out that there is a short circuit between terminal 1 of connector (B) and terminal
1 of connector (C)
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
The suspect circuits or parts for each problem symptom are shown in the table below Use this table totroubleshoot the problem when a rdquoNormalrdquo code is displayed in the diagnostic trouble code check but theproblem is still occurring Numbers in the table indicate the inspection order in which the circuits or partsshould be checkedHINT when the problem is not detected by the diagnostic system even though the problem symptom is
present it is considered that the problem is occurring outside the detection range of the diagnostic system
or that the problem is occurring in a system other than the diagnostic system
bull Circuit Inspection Inspection OrderIndicates the circuit which needs to be checked
for each problem symptom Check in the order inminus
dicated by the numbers
bull Circuit or Part NameIndicates the circuit or part which needs to bechecked
bull PageIndicates the page where the flow chart foreach circuit is located
bull Problem Symptom
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE1 For troubleshooting diagnostic trouble code charts or problem symptom charts are provided for each
circuit with detailed inspection procedures on the following pages
2 When all the component parts wire harnesses and connectors of each circuit except the ECU are
found to be normal in troubleshooting then it is determined that the problem is in the ECU
Accordingly if diagnosis is performed without the problem symptoms occurring the instruction will be
to check and replace the ECU even if the problem is not in the ECU So always confirm that the prominus
blem symptoms are occurring or proceed with inspection while using the symptom simulation
method
3 The instructions rdquoCheck wire harness and connectorrdquo and rdquoCheck and replace ECUrdquo which appear in
the inspection procedure are common and applicable to all diagnostic trouble codes Follow the prominus
cedure outlined below whenever these instructions appear
Check Wire Harness and ConnectorThe problem in the wire harness or connector is an open circuit or a short circuit
OPEN CIRCUITThis could be due to a disconnected wire harness faulty contact in the connector a connector terminal pullminus
ed out etc
HINT
1 It is rarely the case that a wire is broken in the middle of it Most cases occur at the connector In par minus
ticular carefully check the connectors of sensors and actuators
2 Faulty contact could be due to rusting of the connector terminals to foreign materials entering terminus
minals or a drop in the contact pressure between the male and female terminals of the connector Simpminus
ly disconnecting and reconnecting the connectors once changes the condition of the connection anc
may result in a return to normal operation
Therefore in troubleshooting if no abnormality is found in the wire harness and connector check but
the problem disappears after the check then the cause is considered to be in the wire harness or con
nectors
SHORT CIRCUITThis could be due to a short circuit between the wire harness and the body ground or to a short inside the
switch etc
HINT
bull When there is a short between the wire harness and body ground check thoroughly whether the wire
harness is caught in the body or is clamped properly
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
(1) Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connecminus
tor (A) and body ground
In the case of Fig 6
Between terminal 1 of connector (A) and body ground rarr Continuity
Between terminal 2 of connector (A) and body ground rarr No continuity (open)Therefore it is found out that there is a short circuit between terminal 1 of connector (A) and terminal
1 of connector (C)
(2) Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body
ground and terminal 1 of connector (B) and body ground
Between terminal 1 of connector (A) body ground rarr No continuity (open)
Between terminal 1 of connector (B) and body ground rarr Continuity
Therefore it is found out that there is a short circuit between terminal 1 of connector (B) and terminal
1 of connector (C)
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE1 For troubleshooting diagnostic trouble code charts or problem symptom charts are provided for each
circuit with detailed inspection procedures on the following pages
2 When all the component parts wire harnesses and connectors of each circuit except the ECU are
found to be normal in troubleshooting then it is determined that the problem is in the ECU
Accordingly if diagnosis is performed without the problem symptoms occurring the instruction will be
to check and replace the ECU even if the problem is not in the ECU So always confirm that the prominus
blem symptoms are occurring or proceed with inspection while using the symptom simulation
method
3 The instructions rdquoCheck wire harness and connectorrdquo and rdquoCheck and replace ECUrdquo which appear in
the inspection procedure are common and applicable to all diagnostic trouble codes Follow the prominus
cedure outlined below whenever these instructions appear
Check Wire Harness and ConnectorThe problem in the wire harness or connector is an open circuit or a short circuit
OPEN CIRCUITThis could be due to a disconnected wire harness faulty contact in the connector a connector terminal pullminus
ed out etc
HINT
1 It is rarely the case that a wire is broken in the middle of it Most cases occur at the connector In par minus
ticular carefully check the connectors of sensors and actuators
2 Faulty contact could be due to rusting of the connector terminals to foreign materials entering terminus
minals or a drop in the contact pressure between the male and female terminals of the connector Simpminus
ly disconnecting and reconnecting the connectors once changes the condition of the connection anc
may result in a return to normal operation
Therefore in troubleshooting if no abnormality is found in the wire harness and connector check but
the problem disappears after the check then the cause is considered to be in the wire harness or con
nectors
SHORT CIRCUITThis could be due to a short circuit between the wire harness and the body ground or to a short inside the
switch etc
HINT
bull When there is a short between the wire harness and body ground check thoroughly whether the wire
harness is caught in the body or is clamped properly
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
(1) Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connecminus
tor (A) and body ground
In the case of Fig 6
Between terminal 1 of connector (A) and body ground rarr Continuity
Between terminal 2 of connector (A) and body ground rarr No continuity (open)Therefore it is found out that there is a short circuit between terminal 1 of connector (A) and terminal
1 of connector (C)
(2) Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body
ground and terminal 1 of connector (B) and body ground
Between terminal 1 of connector (A) body ground rarr No continuity (open)
Between terminal 1 of connector (B) and body ground rarr Continuity
Therefore it is found out that there is a short circuit between terminal 1 of connector (B) and terminal
1 of connector (C)
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE1 For troubleshooting diagnostic trouble code charts or problem symptom charts are provided for each
circuit with detailed inspection procedures on the following pages
2 When all the component parts wire harnesses and connectors of each circuit except the ECU are
found to be normal in troubleshooting then it is determined that the problem is in the ECU
Accordingly if diagnosis is performed without the problem symptoms occurring the instruction will be
to check and replace the ECU even if the problem is not in the ECU So always confirm that the prominus
blem symptoms are occurring or proceed with inspection while using the symptom simulation
method
3 The instructions rdquoCheck wire harness and connectorrdquo and rdquoCheck and replace ECUrdquo which appear in
the inspection procedure are common and applicable to all diagnostic trouble codes Follow the prominus
cedure outlined below whenever these instructions appear
Check Wire Harness and ConnectorThe problem in the wire harness or connector is an open circuit or a short circuit
OPEN CIRCUITThis could be due to a disconnected wire harness faulty contact in the connector a connector terminal pullminus
ed out etc
HINT
1 It is rarely the case that a wire is broken in the middle of it Most cases occur at the connector In par minus
ticular carefully check the connectors of sensors and actuators
2 Faulty contact could be due to rusting of the connector terminals to foreign materials entering terminus
minals or a drop in the contact pressure between the male and female terminals of the connector Simpminus
ly disconnecting and reconnecting the connectors once changes the condition of the connection anc
may result in a return to normal operation
Therefore in troubleshooting if no abnormality is found in the wire harness and connector check but
the problem disappears after the check then the cause is considered to be in the wire harness or con
nectors
SHORT CIRCUITThis could be due to a short circuit between the wire harness and the body ground or to a short inside the
switch etc
HINT
bull When there is a short between the wire harness and body ground check thoroughly whether the wire
harness is caught in the body or is clamped properly
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
(1) Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connecminus
tor (A) and body ground
In the case of Fig 6
Between terminal 1 of connector (A) and body ground rarr Continuity
Between terminal 2 of connector (A) and body ground rarr No continuity (open)Therefore it is found out that there is a short circuit between terminal 1 of connector (A) and terminal
1 of connector (C)
(2) Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body
ground and terminal 1 of connector (B) and body ground
Between terminal 1 of connector (A) body ground rarr No continuity (open)
Between terminal 1 of connector (B) and body ground rarr Continuity
Therefore it is found out that there is a short circuit between terminal 1 of connector (B) and terminal
1 of connector (C)
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE1 For troubleshooting diagnostic trouble code charts or problem symptom charts are provided for each
circuit with detailed inspection procedures on the following pages
2 When all the component parts wire harnesses and connectors of each circuit except the ECU are
found to be normal in troubleshooting then it is determined that the problem is in the ECU
Accordingly if diagnosis is performed without the problem symptoms occurring the instruction will be
to check and replace the ECU even if the problem is not in the ECU So always confirm that the prominus
blem symptoms are occurring or proceed with inspection while using the symptom simulation
method
3 The instructions rdquoCheck wire harness and connectorrdquo and rdquoCheck and replace ECUrdquo which appear in
the inspection procedure are common and applicable to all diagnostic trouble codes Follow the prominus
cedure outlined below whenever these instructions appear
Check Wire Harness and ConnectorThe problem in the wire harness or connector is an open circuit or a short circuit
OPEN CIRCUITThis could be due to a disconnected wire harness faulty contact in the connector a connector terminal pullminus
ed out etc
HINT
1 It is rarely the case that a wire is broken in the middle of it Most cases occur at the connector In par minus
ticular carefully check the connectors of sensors and actuators
2 Faulty contact could be due to rusting of the connector terminals to foreign materials entering terminus
minals or a drop in the contact pressure between the male and female terminals of the connector Simpminus
ly disconnecting and reconnecting the connectors once changes the condition of the connection anc
may result in a return to normal operation
Therefore in troubleshooting if no abnormality is found in the wire harness and connector check but
the problem disappears after the check then the cause is considered to be in the wire harness or con
nectors
SHORT CIRCUITThis could be due to a short circuit between the wire harness and the body ground or to a short inside the
switch etc
HINT
bull When there is a short between the wire harness and body ground check thoroughly whether the wire
harness is caught in the body or is clamped properly
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
(1) Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connecminus
tor (A) and body ground
In the case of Fig 6
Between terminal 1 of connector (A) and body ground rarr Continuity
Between terminal 2 of connector (A) and body ground rarr No continuity (open)Therefore it is found out that there is a short circuit between terminal 1 of connector (A) and terminal
1 of connector (C)
(2) Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body
ground and terminal 1 of connector (B) and body ground
Between terminal 1 of connector (A) body ground rarr No continuity (open)
Between terminal 1 of connector (B) and body ground rarr Continuity
Therefore it is found out that there is a short circuit between terminal 1 of connector (B) and terminal
1 of connector (C)
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
(1) Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connecminus
tor (A) and body ground
In the case of Fig 6
Between terminal 1 of connector (A) and body ground rarr Continuity
Between terminal 2 of connector (A) and body ground rarr No continuity (open)Therefore it is found out that there is a short circuit between terminal 1 of connector (A) and terminal
1 of connector (C)
(2) Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body
ground and terminal 1 of connector (B) and body ground
Between terminal 1 of connector (A) body ground rarr No continuity (open)
Between terminal 1 of connector (B) and body ground rarr Continuity
Therefore it is found out that there is a short circuit between terminal 1 of connector (B) and terminal
1 of connector (C)
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
(1) Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connecminus
tor (A) and body ground
In the case of Fig 6
Between terminal 1 of connector (A) and body ground rarr Continuity
Between terminal 2 of connector (A) and body ground rarr No continuity (open)Therefore it is found out that there is a short circuit between terminal 1 of connector (A) and terminal
1 of connector (C)
(2) Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body
ground and terminal 1 of connector (B) and body ground
Between terminal 1 of connector (A) body ground rarr No continuity (open)
Between terminal 1 of connector (B) and body ground rarr Continuity
Therefore it is found out that there is a short circuit between terminal 1 of connector (B) and terminal
1 of connector (C)
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
(1) Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connecminus
tor (A) and body ground
In the case of Fig 6
Between terminal 1 of connector (A) and body ground rarr Continuity
Between terminal 2 of connector (A) and body ground rarr No continuity (open)Therefore it is found out that there is a short circuit between terminal 1 of connector (A) and terminal
1 of connector (C)
(2) Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body
ground and terminal 1 of connector (B) and body ground
Between terminal 1 of connector (A) body ground rarr No continuity (open)
Between terminal 1 of connector (B) and body ground rarr Continuity
Therefore it is found out that there is a short circuit between terminal 1 of connector (B) and terminal
1 of connector (C)
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
(1) Disconnect connectors (A) and (C) and measure the resistance between terminals 1 and 2 of connecminus
tor (A) and body ground
In the case of Fig 6
Between terminal 1 of connector (A) and body ground rarr Continuity
Between terminal 2 of connector (A) and body ground rarr No continuity (open)Therefore it is found out that there is a short circuit between terminal 1 of connector (A) and terminal
1 of connector (C)
(2) Disconnect connector (B) and measure the resistance between terminal 1 of connector (A) and body
ground and terminal 1 of connector (B) and body ground
Between terminal 1 of connector (A) body ground rarr No continuity (open)
Between terminal 1 of connector (B) and body ground rarr Continuity
Therefore it is found out that there is a short circuit between terminal 1 of connector (B) and terminal
1 of connector (C)
minusINTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLEDSYSTEMS
